Recently, as a buffer device for absorbing a shock felt by a rider of a motorcycle or the like, a body wear which incorporates an air inflating chamber (air bag) therein, that is, an air bag jacket has been proposed. For example, Japanese Utility Model Registered Publication 3068775 discloses an air bag having the structure of an inflator in which a compressed air tank is connected to one end of a ventilation valve mounted on a connector communicating with the inside of an air bag, and a sealed port of the compressed air tank is broken using a piercing needle in response to a shock felt by a rider thus rapidly introducing air in the inside of the compressed air tank into the inside of the air bag.